1. Field of the Invention
The present invention is concerned with a novel process for producing keptopantolactone(dihydro-4,4-dimethyl-2,3-furandione).
2. Description of the Prior Art
Ketopantolactone is an important starting material for manufacturing optically active pantolactone (dihydro-3-hydroxy-4,4-dimethyl-2(3H)-furanone), which is used in the manufacture of biologically active pantothenic acid.
Several prior art processes for producing ketopantolactone are known. In the prior art, racemic pantolactone was oxidized to ketopantolactone by utilizing lead tetraacetate, N-bromosuccinimide or chromium trioxide (Jones' reagent) as the oxidizing agent. This prior art procedure disadvantageously resulted in relatively low yield of ketopantolactone, and the oxidizing agent was expensive. In the prior aer, this process has been modified by using bromine or alkali or alkaline earth metal hypochlorites in the organic phase.
In another prior art process, dimethylpyruvic acid and formaldehyde were utilized to manufacture ketopantolactone. Disadvantageously this process also suffered from obtaining only relatively low yields and its end product was not entirely pure even after distillation.